1. Field of the Invention
The present invention relates to a light emitting diode (LED) backlight module and a method for eliminating shadow noise, and more particularly, to a backlight module with a support pin and a method for eliminating shadow around the support pin of an LED backlight.
2. Description of the Related Art
Currently, liquid crystal display (LCD) backlights in common use include cold cathode fluorescent lamps (CCFLs) and LEDs. It has a great opportunity for the LED type to prevail in the competition due to the advantages in environmental protection and color brightness. Especially when applied in the area of high contrast LCD, the high brightness of LED is far more desirable than that of CCFL.
In conventional LCDs, either with CCFLs or LED backlights, the whole backlight modules are controlled collectively instead of locally or independently. Additionally, in conventional LCDs, optical films on a backlight module usually have superior light diffusion quality to attain a uniform backlight behavior. In high contrast LCD application, however, to achieve a better contrast (beyond 10000:1, for example), the methodology about backlight control and the criteria for selecting optical film may be totally different. For example, luminance of an individual LED is usually controlled independently, and the criteria for a feasible optical film tends to require better local brightness instead of global uniformity.
An LCD device with LED backlight generally needs to install several support pins in between the backlight and the optical plate, so as to keep a uniform distance all over therebetween. In such a high contrast large scale LCD, it is inevitable that some shadow effect may arise on the panel area around a support pin as a result of random light refraction and reflection which in turn is due to non-uniform luminance of LEDs surrounding the support pin as well as the shade of the support pin itself. Independent control of backlight LEDs and locally concentrative brightness of optical films should also account for the undesirable noises produced in the shadow effect.
FIG. 1 illustrates the relative location about a typical support pin and the surrounding LEDs within a backlight module under an optical plate. Specifically, what shown in FIG. 1 includes a support pin 10, a plurality of LEDs 20, and an optical plate 90. As shown in FIG. 1, the support pin 10 is located among four backlighting LEDs 20 so as to keep a uniform distance between the optical plate 90 and the backlight therebelow. Obvious shadow noise will appear on the panel area near the support pin 10 as mentioned above. The shadow noise in turn downgrades the quality of images displayed nearby the support pin 10.